This invention relates generally to catalysts and, more specifically to the preparation and characterization of Cu—Al—O catalysts to replace Cu/Cr catalysts in specific applications.
The commercial catalysts for hydrogenolysis of carbonyl groups in organic compounds have been dominated by Adkins' catalyst since the 1930's (H. Adkins, R. Connor, and K. Folkers, U.S. Pat. No. 2,091,800 (1931)). The Adkins' catalyst is a complex mixture of primarily copper oxide and copper chromite. The catalyst is used in hydrogenolysis reactions, for example the catalytic hydrogenolysis of an ester to alcohols, illustrated generally by the following reaction: 
Under reaction conditions it is believed that the catalyst reduces to a mixture of metal copper, cuprous oxide and copper chromite. One of the crucial roles of chrome in Cu/Cr catalysts is that it behaves as a structural promoter.
The Cu/Cr catalysts have widespread commercial and industrial application in such diverse processes as hydrogenation of aldehyde in oxoalcohol finishing, hydration of acrylonitrile, fatty acid hydrogenolysis, hydrogenolysis of methyl esters, reductive amination, and a myriad of other hydrogenation and oxidation reactions such as are listed below. U.S. Pat. No. 3,935,128, to Fein et al, provides a process for producing a copper chromite catalyst. U.S. Pat. No. 4,982,020 to Carduck et al., discloses a process for direct hydrogenation of glyceride oils where the reaction is carried out over a catalyst containing copper, chromium, barium and/or other transition metals in the form of oxides which, after calcination, form the catalyst mass. U.S. Pat. No. 4,450,245 to Adair et al., provides a catalyst support wherein the catalyst is employed in the low temperature oxidation of carbon monoxide, another important application of such catalysts.
Environmental issues involving disposal of chrome-containing catalysts, however, are expected to eventually eliminate their use in many countries. Additionally, catalyst activity is one of the most important factors determining a catalyst's performance. It is, therefore, advantageous to employ non-chrome, copper-containing catalysts having good catalyst activity to replace currently used Cu/Cr catalysts in hydrogenation, alkylation and other reactions.
Several prior art, non-chrome containing catalysts are known. For example, U.S. Pat. No. 5,418,201, to Roberts et al., discloses hydrogenation catalysts in powdered form and method of preparing hydrogenation catalysts comprising oxides of copper, iron, aluminum and magnesium. U.S. Pat. No. 5,243,095 also to Roberts et al. provides for the use of such copper, iron, aluminum, and magnesium catalysts in hydrogenation conditions.
U.S. Pat. No. 4,252,689 to Bunji Miya, describes a method of preparing a copper-iron-alumina catalyst used in hydrogenation. U.S. Pat. No. 4,278,567 to Bunji Miya et al., discloses a similar process for making a copper-iron-aluminum catalyst. U.S. Pat. No. 4,551,444 to Fan-Nan Lin et al., provides a five-component catalyst wherein the essential components are copper, an iron group component, a component of elements 23-26, an alkali metal compound and a precious metal compound.
C. W. Glankler, Nitrogen Derivatives (Secondary and Tertiary Amines, Quaternary Salts, Diamines, Imidazolines), J. Am. Oil Chemists' Soc., November 1979 (Vol 56), pages 802A-805A, shows that a copper-chromium catalyst is used to retain carbon to carbon unsaturation in the preparation of nitrogen derivatives.
U.S. Pat. No. 4,977,123 to Maria Flytzani Stephanopoulos et al., discloses extruded sorbent compositions having mixed oxide components of copper oxide, iron oxide, and alumina. U.S. Pat. No. 3,865,753, to Broecker et al, provides a process for preparing a nickel magnesium aluminum catalyst used for the cracking of hydrocarbons. The prior art, non-chrome containing catalysts have several disadvantages that limit the industrial applicability of the catalysts.
An ideal catalyst should be both chemically and physically stable. Chemical stability is demonstrated by consistent catalyst activity in an acceptable time period. Physical stability is demonstrated by maintaining a stable particle size or physical form during the chemical reaction. Moreover, an ideal catalyst would have narrow particle distribution since particle size affects filtration speed in a commercial process employing the catalysts. The stability is further demonstrated by resistance to common poisons such as sulfur compounds, organic chlorines, bromine and iodine compounds. Generally, stability is tested using Cu/Cr catalyst as the standard catalyst.
An ideal catalyst also would have a low percentage of leachable cations. This ensures the maintenance of catalyst activity and a good product quality.
Furthermore, it is important the catalyst function well in commercial applications. For example, the hydration of acrylonitrile to acrylamide over a copper-containing catalyst is an important industrial application. Several different copper catalysts have been developed for this application, as indicated by the prior art patents. The catalysts include copper/chrome, copper/silica, copper on kieselguhr, Raney copper, ion exchange copper on silica and copper on alumina catalysts. Most of the prior art catalysts used in this application have the problem of deactivation. The catalyst is deactivated by the accumulation of polyacrylamide on the surface or by the oxidation of surface copper. Selectivity is also important. Normally, hydration of C—N bonds is favored by acidic oxides while hydrolysis of C—C bonds is favored by basic oxides. Therefore, the surface acidity of the catalyst is crucial to this application.
For some other applications that require some surface basicity, alkaline metal or alkaline metal compounds should be remained or added to the catalyst matrix.